The present invention relates generally to tumbler wheel type lock mechanisms. More particularly, the present invention relates to tumbler wheel type locks for use in high security applications such as securing safe vault doors and other high strength relatively large doors.
Tumbler wheel locks generally include three or more tumbler wheels having peripheral notches or gates. The tumbler wheels are supported for individual rotation about a common axis. A combination wheel or key is used to rotate the tumbler wheels to align the gates. A lock actuation lever is provided having a fence on one end with the other end of the lever being attached to the lock bolt. A control cam is typically mounted on the same common axis with the tumbler wheels. The control cam includes a gate designed to engage a latch on the lever to provide cam operated movement of the lock bolt between extended and retracted positions. The lever is continually biased towards the tumbler wheels and control cam so that the latch continually rides on the peripheral surface of the control cam. The latch can only fall into and engage the gate on the control cam when the tumbler wheel gates are aligned. The control cam gate and latch on the lever are designed so that as the lever and attached latch bolt are extended, the latch is forced out of the cam gate. An example of this type of lock is shown in U.S. Pat. No. 3,991,596 issued to Klaus W. Gartner on Nov. 16, 1976.
Although many of the tumbler locks in existence are well suited for their intended purpose, it still would be desirable to increase the tamper resistance of the locks, simplify the lock mechanism and increase precision with which the lock bolt is extended and retracted to reduce hang up problems experienced during installation and operation of the lock assembly. For example, during installation and operation of the lock, it is important that the extension and retraction of the lock bolt be maintained within close tolerances. Otherwise, possible binding and jamming of the lock bolt may occur. This is especially important for large safe doors where inadvertent jamming of the lock bolt during installation or operation would require structural disassembly of the vault structure. The removal of a jammed lock bolt from large safe doors is many times difficult if not impossible without structurally damaging the vault structure. It therefore is desirable to provide a lock mechanism in which the extension and retraction of the lock bolt is controlled within close tolerances to reduce the chances of inadvertent lock bolt jamming during installation and operation of the lock.
The control cam gate must necessarily be slanted to provide hooking of the lever latch to pull the lever and attached lock bolt to the retracted position. Also, the slanted cam gate is necessary to force the lever latch out of the gate when the lever and attached lock bolt are moved to their extended positions. When the lever latch is forced upward and out of the cam gate upon extension of the latch bolt, the fence on the latch is also moved upward and out of the aligned tumbler wheel gates. Many times it is desirable to retract the latch bolt after an initial latch bolt extension without first scrambling and realigning the tumbler wheel gates. In such cases when the tumbler wheel gates are left in their aligned position after latch bolt extension, the fence tends to hang up on the forward edge of the tumbler wheel gates when the cam gate is realigned with the lever latch for latch bolt retraction. It would be desirable to provide some way of preventing such fence hang ups from occurring.
Most tumbler type combination locks utilize a spring of some type to bias the lever towards the tumbler wheels and cam wheel. Typically, the lever is rotatably mounted to the lock bolt using a standard machine bolt or screw. The lever biasing spring is also mounted on the mounting bolt. During continual extension and retraction of the lock bolt, the bolt or screw used to mount the lever to the lock bolt can eventually vibrate losse and cause jamming and/or damage of the lock assembly. It would be desirable to improve the way in which the lock lever is mounted to the lock bolt and biased towards the tumbler wheels and cam wheel.
Conventional tumbler wheel lock assemblies for high security applications include a high strength housing which includes a removable backplate. When the backplate is removed, access is provided to all portions of the lock housing to allow access for assembly and repair of the lock mechanism. A typical technique utilized by safecrackers to overcome combination locks is to drill through the tumbler wheels and forceably punch the backplate from the housing. Special tools are then used to gain access from the rear of the lock to the lock bolt and other lock assembly parts. To guard against this type of safe cracking technique, relock springs or other relock devices are provided which lock or otherwise connect the lock bolt to the housing when the backplate is removed. It would be desirable to provide an improved relock spring assembly which provides improved blocking of the lock bolt and is tamper resistant.